Zero valent materials, usually metallic, are useful in providing thin films or pigments. These applications yield items that display electrical, thermal, decorative, reflectance, corrosion inhibiting, antifouling, and many other properties. Some articles of commerce using these approaches include mirrors, microwave susceptor food packaging, conductive tapes as burglar alarm systems on windows and doors, decorative cabinets, automotive, and plumbing fixtures, holographic laminates as security and advertising items, sacrificial metallic corrosions to give corrosion and wear protection, and magnetic coatings which contain bits of information or provide recording tape performance.
Zero valent materials are affixed or plated onto a variety of substrates such as paper, plastic, glass, ceramics, rubbers, and other metals. The processes used to affix the zero valent (free) metals include cladding, electrochemical deposition, electroplating, electroless plating, electrophoretic deposition,, flame spraying, sputtering, and vacuum vapor deposition. Such processes can be subject to certain deficiencies such as restrictions on the size or geometry of the item to be plated. In some cases, the plating cannot be placed on specific portions of the substrate unless masking is initially performed.
Nonmetallic, competitive materials include carbon black and conductive polymers. Carbon can be subject to problems associated with coloring the article in a color other than black. The conductive polymer approach consists of modifying the intrinsic bulk properties of a polymer by processing, especially by pyrolysis, and another approach focuses on increasing the electrical conductance of conjugated polymers (i.e., polymers which already have at least some electrical conductance) at the molecular level by controlled incorporation of molecular dopants that may or may not form charge-transfer complexes with the host conjugated polymer. Still another approach is to attain the desired conductivity by incorporating macroscopic pieces of conducting material (metal flakes, carbon-black particulates, or carbon fibers, for example) in host polymers to form conducting composites. Some of these conductive polymers are not amenable to aqueous systems; they are either subject to air quality emissions restrictions during the drying or removing of their solvents, or are wholly intractable toward all solvents.
In most cases, after the zero valent material is affixed to the substrate, a coating is applied as an overcoating. The overcoatings give protection and/or adhesive properties which help to increase the lifetime of the zero valent system under operating conditions. The process of applying a coating over the zero valent material requires a second step in the preparation (manufacturing) of the article.
A latex of a polymer contains a polymer dispersed (typically emulsified) and stabilized in aqueous media. In contrast to water-soluble polymers which are not prepared in aqueous media (although soluble therein), the polymers dispersed in a latex are typically formed in the aqueous medium. Whereas water soluble salts have been readily soluble in aqueous media containing such water soluble polymers, incorporation of significant concentrations of salts or highly acidic material into a latex without coagulation has been an ongoing problem. Achievement of electrical conductivity associated with latex-based coatings, binders and adhesives has likewise been a difficult task, particularly since latex polymers are not conjugated (i.e., are considered insulators), and more particularly since at least two steps have been required during preparation.